1. Field of the Invention
The present invention relates to an integrated steering gear and frame structure, and more particularly to an integrated steering gear and frame structure, in which a sub-frame as a suspension system and a steering gear as a steering system are modularized.
2. Description of the Related Art
In general, a steering system is a machine by which a vehicle is steered to be turned to follow the desired traveling course of its driver, and is composed of a manipulation mechanism having a steering wheel, a steering shaft, a steering column, etc. so as to transmit a manipulation force caused by a direct steering manipulation of the driver to a steering gear, a linkage and so on, a gearing for decreasing rotation of the steering shaft to increase the manipulation force and simultaneously changing movement direction of the manipulation mechanism to transmit the changed movement direction to a link mechanism. The gearing typically makes much use of a rack-pinion mode, and particularly a rack-pinion steering gear is housed in a steering gear box, which is stably mounted to a vehicular body via mounting brackets.
One of conventional structures for mounting the steering gear to the vehicular body is shown in FIG. 1. In particular, FIG. 1 shows a conventional rack-pinion steering gear mounting structure. As shown in FIG. 1, two upper and lower steel plates are pressed in a specific shape and are welded to form a sub-frame 100 in a tube shape. A steering gear box 200 is fixed to the upper steel plate 110 of the sub-frame 100 by mounting brackets 150 and 170. The steering gear box 200 is provided with a rack bar through-hole through which a rack bar is inserted, a pinion housing 210 into which a pinion is inserted, and a yoke part insertion part 230 into which a yoke part is inserted, as well as is assembled by inserting the rack bar, the pinion and the yoke part. Meanwhile, both ends of the sub-frame 100 are formed with mounting parts 130 for fixture with the vehicular body and are connected to the vehicular body. Further, both ends of the sub-frame 100 are connected with control arms 300, which constitute the suspension system and are adjacent to the mounting parts. In this manner, the sub-frame 100 and the steering gear box 200 are separately prepared and assembled.
Meanwhile, another conventional rack-pinion steering gear is disclosed in Korean Patent Publication No. 2003-0006651. FIG. 2 is a cross-sectional view showing the conventional rack-pinion steering gear. As shown in FIG. 2, in a steering gear box 1, a pinion 2 mounted to a leading end of the steering shaft is meshed with a rack 3, and thus rotation of the pinion 2 causes the rack 3 to move in a transverse direction. The transverse movement of the rack 3 is transmitted to a steering shaft and a tie rod coupled to both ends of the rack 3 by a ball joint. The coupling of the pinion 2 and rack 3 in the steering gear box 1 is designed to adjust a clearance through a rack guide 6 and a nut 7. The rack guide 6 is recessed in a semi-cylindrical shape on its side so that the rack 3 meshed with the pinion 2 and moving in the transverse direction is supported on the side of the pinion 2. The rack guide 6 is inserted into one end of the steering gear box 1. The nut 7 is threaded on its inner circumferential surface so as to position and fix the rack guide 6, and is formed with a bolt head 8 on its outer side so as to be screwed to one end of the steering gear box 1. Further, the other side of the rack guide 6 is formed with a recess, and endows a damping force to contact surfaces between the rack guide 6 and the nut 7 between which a spring 10 is interposed. Therefore, it is possible to adjust a meshed state of the pinion 2 and the rack 3 either by inserting the nut 7 to cause the rack guide 6 to close contact the rack 3 on the side of the pinion 2 via the spring 10 or by retreating the nut 7.
However, the structure mounting the steering gear to the vehicular body as mentioned above has the following problems.
The sub-frame as the suspension system and the steering gear as the steering system are manufactured separately by their manufacturers, and are supplied to a module manufacturing firm or a vehicular manufacturing firm.
In this manner, the sub-frame and the steering gear are supplied to the module manufacturing firm or the vehicular manufacturing firm, and then are assembled by bolts or in another fastening method. The assembly is mounted to the vehicle.
Because the sub-frame and the steering gear are fastened by bolts or in another fastening method, some portions are overlapped to cause an assembling tolerance. Further, each of the sub-frame and the steering gear incurs a physical distribution cost.
Further, the production process by nature causes the sub-frame and the steering gear to be separately manufactured and assembled, so that a rate of generating manufacturing and assembling tolerances is increased.
Because the sub-frame and the steering gear are counterparts to each other, there is inconvenience in that each must be managed in tolerance, production and quality.